POSTED: Tuesday, July 31, 2012 - 1:30pm
UPDATED: Tuesday, July 31, 2012 - 4:45pm
LONDON (CNN) — History has already been made once at the Olympics on Tuesday, and Michael Phelps of the United States will be aiming to make it a twofer later in the day as he seeks a record-breaking 19th Olympic gold.
Queen Elizabeth's equestrian granddaughter Zara Phillips put her name in the record books earlier in the day by becoming the first member of the British royal family to win an Olympic medal. She claimed a silver as part of the British eventing team. Her mother Princess Anne, a 1976 Olympic equestrian, draped the medal around her neck.
Another British Olympian, Tom Daley, was in the news for a less happy reason as police arrested a 17-year-old accused of abusing the teen diver in comments on Twitter.
1) MEN'S SWIMMING
Phelps will try to become the most decorated Olympian in history when he competes in two races -- the 200-meter butterfly and the men's 4x200-meter freestyle relay.
One more medal would tie Phelps with Larisa Latynina, a Soviet-era gymnast who has 18 Olympic medals; a second medal for Phelps would break the record.
Latynina, 77, will be on hand to watch Phelps swim Tuesday.
2) WOMEN'S GYMNASTICS
Four years after China won at home, the United States is a favorite to win the team final Tuesday. A U.S. victory would be the first since 1996, when a badly limping Kerri Strug famously helped secure a team gold medal with her final vault.
This time, the Americans will rely on world all-around champion Jordyn Wieber to bounce back from Sunday's personal devastation of not qualifying for the individual all-around final.
3) WOMEN'S SWIMMING
Chinese teen phenom Ye Shiwen is favored to win the 200-meter individual medley, three days after she broke a world record winning the 400-meter individual medley. Ye's final 50-meter freestyle of that race was faster than that of American Ryan Lochte, who won gold in the men's 400-meter individual medley.
Another teen sensation, 17-year-old Missy Franklin of the United States, will take on world-record holder Federica Pellegrini of Italy in the 200-meter freestyle race.
4) POWERHOUSE TEAMS FACE OFF IN VOLLEYBALL, WATER POLO
In two matchups of world powers, Brazil and Russia will battle in a preliminary men's volleyball game, and Spain and Croatia will duke it out in a preliminary round of men's water polo.